
80
μ
PD75237
(1)
Serial interface (channel 0) functions
The following four modes are available for the
μ
PD75237 serial interface (channel 0).
The functions of each mode are outlined below.
Operation stop mode
This is the mode used when no serial transfer is performed. Low power consumption operation is
possible in this mode.
3-wire serial I/O mode
8-bit data is transferred using three lines of serial clock (SCK0), serial output (SO0) and serial input
(SI0).
The 3-wire serial I/O mode enables simultaneous transmission/reception, thus shortening the data
transfer processing time.
Since the start bit of 8-bit data for serial transfer can be switched between MSB and LSB, channel 0
can be connected to a device having either start bit.
In the 3-wire serial I/O mode, channel 0 can be connected to the 75X series, 78K series and various
types of peripheral I/O devices.
2-wire serial I/O mode
8-bit data is transferred using two lines of serial clock (SCK0) and serial data bus (SB0 or SB1).
Communication is possible with two or more devices by controlling the level of output to the two lines
by software.
Since the output level of SCK0 and SB0 (or SB1) can be controlled by software, any transfer format
is applicable. Thus, the number of handshake lines previously required to connect two or more devices
can be decreased and so the input/output ports can be used efficiently.
SBI mode (serial bus interface mode)
This mode enables communication with two or more devices with two lines of serial clock (SCK0) and
serial data bus (SB0 or SB1).
This mode is compliant with the NEC serial bus format.
In the SBI mode, the transmitter can output an “address” for selection of a serial communication target
device on the serial data bus, a “command” to provide instructions to the target device and actual “data”.
The receiver can distinguish between “address”, “command” and “data” by hardware. As in the 2-
wire serial I/O mode, this function enables the input/output ports to be used efficiently and the serial
interface control portions of any applied program to be simplified.
(2)
Serial interface (channel 0) configuration
Fig. 4-39 is a block diagram of serial interface (channel 0).